The present invention is directed to a method and to a circuit arrangement for transmitting message cells within an ATM network.
A method for forwarding message cells, which have a cell headier identifying the respective virtual connection and which are transmitted on offering trunks during the course of virtual connections according to an asynchronous transfer method via cell switching equipment having at least two redundant switching matrices, to serving trunks is already known (European Patent Application 89 10 3798 corresponding to U.S. Ser. No. 08/040,913 filed Mar. 29, 1993). In this known method, a message cell group having a plurality of identical message cells corresponding in number to the plurality of redundant switching matrices is formed by duplication for every one of the message cells transmitted on one of the offering trunks during the course of a virtual connection. An identical auxiliary identifier in the form of a continuously assigned message cell sequence number that changes for successive message cell groups is thereby entered into the cell header of each of the message cells of a message cell group. Subsequently, the message cells of a message cell group are separately transmitted via the redundant switching matrices in the direction of the serving trunk for the respective virtual connection. Finally, after such a transmission via the redundant switching matrices, only one of the message cells a message cell group is forwarded to the serving trunk coming into consideration. It is forwarded thereto on the basis of the auxiliary identifier respectively attached to the message cells.
Furthermore, a method has already been proposed (European Patent Application 91 10 7434 corresponding to U.S. Ser. No. 07/880,188 now U.S. Pat. No. 5,317,561 filed May 5, 1992) for switching message cells of a transmission system transporting a message cell stream according to an asynchronous transfer method via a switching network constructed with modules. The transport bit rate of the transmission system is a multiple of the transmission bit rate of the switching elements of the modules. Messages to be switched are thereby distributed onto a plurality of switching network inputs corresponding to the multiple, upon respective attachment of information. Such information identifies all those modules via which the message cells are to be through-connected to an output of the switching network. The message cells transmitted to various outputs are then recombined to form a message cell stream. What is thereby provided, among other things, is that a cyclically continuous sequence number is attached in call-associated fashion to the message cells before the through-connection through the switching network. The sequence of the message cells for every connection is assured on the basis of this sequence number in the combination to form the message cell stream. The message cells are cyclically distributed onto the switching network inputs.